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Community Horticulture Fact Sheet #07
Using Transplants
Two secrets of productive gardening are:
-Always have plenty of young seedlings around to fill in empty spots in your garden (for example, where carrots did not come up well, or where slugs ate half your spinach seedlings).
-Grow early and late (fall-winter) crops using varieties selected for these seasons. The key to putting both of these secrets to work for you is to start as many crops as possible indoors in containers (or outside in a cold frame) to be transplanted into the garden when you need them. Using transplants gives you a two-week to two-month head start in the spring plus a big jump on succeeding crops, since you always have established plants to put into the garden instead of just seeds. Also, you can grow the crops and varieties you like, including over-winter crops. Stores offer only limited varieties of a few kinds of vegetables, a few weeks of the year. See Community Horticultural Fact Sheet #8 for a chart listing suggested timing for various crops.
Where to Start Seeds
Warmth and moisture are more important than direct light for sprouting seeds. Once seedlings are up though, they should be moved to a place that gets at least six hours of direct sunlight a day. A large south window should be fine or plants can be moved to a cold frame, if the weather is not too cold. If plants lean dramatically towards the window and get spindly, fluorescent lights may be the answer. A four-foot long, two-bulb fixture is adequate for two full nursery flats of plants. 40-watt cool white bulbs are as good as or better than gro-light bulbs and cheaper. These lights are not as strong as sunlight! They should be kept 2-3 inches away from the tops of the plants (mounting them with link chains allows easy movement) and be kept on 16-18 hours a day. Ideal temperatures for most seeds are 65 to 75 degrees in the daytime and around 10 degrees cooler at night. If the spot you have picked is cold, heating cables or pads may be placed under containers or in flats to maintain 70-degree temperatures.
Soil and Containers
Do not start seed in garden “dirt”. The best recommendation for a seed starting mix is a 1:1 mix of coarse sand and sphagnum peat. (If you cannot get “coarse” sand, which feels really gritty, two parts of finer sand can be used with one part peat.) I like to mix in an equal part of well-decomposed sifted compost or horse manure. If you can get some good compost, use it. As a safety measure, you can kill most diseases in compost by baking it in a 2-3 inch layer at 200 degrees F. until the center of the soil is 140 degree F. for 30 minutes. Add about 1/4 cup of 5:10:10 fertilizer, or about 1/4 cup of bone meal, and 1/8-cup dolomite lime to each 2-3 gallons of mix.
Anything that will hold soil and water and has holes in the bottom/lower sides to let water out is suitable for starting seeds. Shallow (3-4 inches deep) containers are best for easy transplanting. Paper or styrofoam cups, plastic pots, “6-packs” and cut-off milk cartons are all good. Plastic nursery flats are good for holding or moving many smaller containers, or for growing larger crops. Be sure to get flats without holes if you need to catch drainage water. Double up you flats for strength.
Sowing Seed and Watering
Plant seeds 2-3 times as deep as they are wide. Most of the vegetable seeds you will start inside should be planted 1/8 to ¼ inch deep. Sow seeds in rows or “drills” 1-2 inches apart made with a knife or finger. Smooth soil out after seeds are in place. Another method is to scatter seeds evenly over the surface and then sift or scatter a 1/8-inch layer of sand/peat mix over them.
Seeds must be kept moist to sprout, but the surface of the soil should not be kept soaked or fungal diseases may be a problem. To avoid uncovering the seeds, water gently using a fine watering can or a mister. Make sure that the water goes all the way through the soil; don’t just wet the surface. A few tricks to maintaining moisture are:
Cover seed flats with glass or plastic. Keep the covering supported above the soil and seedlings. Place soil-filled containers, with holes in the sides near the bottoms, into pans/tubs with an inch or so of water in the bottom. Water will move up through the soil.
Thinning and Transplanting
Once they are up, seedlings need some room to grow. Most plants should be thinned to 1 or 1 ½ inches apart as soon as they sprout, and then planted out when they grow crowded at this spacing. (Onions and leeks may be grown closer together.)
Seedlings that are going to be “grown-on” in containers, such as tomatoes, peppers, broccoli and cabbage, should be transplanted when they have one true leaf (not seed leaves). Use a soil mix with fertilizer and compost, if possible, for transplants. Always handle young seedlings by the seed leaves only! Transplant them buried up to the seed leaves, 2-3 inches apart in flats or in individual 3-4 inch pots. Cole crops (cabbage, broccoli) should be put out in the garden with 3 to 5 true leaves. Tomatoes, peppers and celery should not go out until night temperatures stay about 55 degrees F. You may have to transplant these crops a second time into larger containers before putting them in the ground, or plant them with some protection from the cold.
Prepared by Holly S. Kennel, Area Extension Agent (3/98).
Reviewed by Joan Helbacka, King County Master Gardener Program Coordinator (3/02)
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